Arithmetic Extension Gate (#10)

* initial commit for arithmetic extension gate

* fixed bug

* added regex for arithmeticExtensionGate

field/field.go

@@ -10,6 +10,7 @@ import (
 type EmulatedField = emulated.Goldilocks
 type F = emulated.Element[EmulatedField]
 type QuadraticExtension = [2]F
+type QEAlgebra = [2]QuadraticExtension
 type Hash = [4]F
 
 var TEST_CURVE = ecc.BN254

field/quadratic_extension.go

@@ -154,6 +154,20 @@ func (c *QuadraticExtensionAPI) AssertIsEqual(a, b QuadraticExtension) {
 	}
 }
 
+func (c *QuadraticExtensionAPI) InnerProductExtension(constant F, startingAcc QuadraticExtension, pairs [][2]QuadraticExtension) QuadraticExtension {
+	acc := startingAcc
+
+	for i := 0; i < len(pairs); i++ {
+		a := pairs[i][0]
+		b := pairs[i][1]
+		mul := c.ScalarMulExtension(a, constant)
+		mul = c.MulExtension(mul, b)
+		acc = c.AddExtension(acc, mul)
+	}
+
+	return acc
+}
+
 func (c *QuadraticExtensionAPI) Println(a QuadraticExtension) {
 	fmt.Print("Degree 0 coefficient")
 	c.fieldAPI.Println(a[0])
@@ -161,3 +175,53 @@ func (c *QuadraticExtensionAPI) Println(a QuadraticExtension) {
 	fmt.Print("Degree 1 coefficient")
 	c.fieldAPI.Println(a[1])
 }
+
+func (c *QuadraticExtensionAPI) MulExtensionAlgebra(a, b QEAlgebra) QEAlgebra {
+	var inner [2][][2]QuadraticExtension
+	var inner_w [2][][2]QuadraticExtension
+	for i := 0; i < 2; i++ {
+		for j := 0; j < 2-i; j++ {
+			idx := (i + j) % 2
+			inner[idx] = append(inner[idx], [2]QuadraticExtension{a[i], b[j]})
+		}
+		for j := 2 - i; j < 2; j++ {
+			idx := (i + j) % 2
+			inner_w[idx] = append(inner_w[idx], [2]QuadraticExtension{a[i], b[j]})
+		}
+	}
+
+	var product QEAlgebra
+	for i := 0; i < 2; i++ {
+		acc := c.InnerProductExtension(NewFieldElement(7), c.ZERO_QE, inner_w[i])
+		product[i] = c.InnerProductExtension(ONE_F, acc, inner[i])
+	}
+
+	return product
+}
+
+func (c *QuadraticExtensionAPI) ScalarMulExtensionAlgebra(a QuadraticExtension, b QEAlgebra) QEAlgebra {
+	var product QEAlgebra
+	for i := 0; i < 2; i++ {
+		product[i] = c.MulExtension(a, b[i])
+	}
+
+	return product
+}
+
+func (c *QuadraticExtensionAPI) AddExtensionAlgebra(a, b QEAlgebra) QEAlgebra {
+	var sum QEAlgebra
+	for i := 0; i < 2; i++ {
+		sum[i] = c.AddExtension(a[i], b[i])
+	}
+
+	return sum
+}
+
+func (c *QuadraticExtensionAPI) SubExtensionAlgebra(a, b QEAlgebra) QEAlgebra {
+	var diff QEAlgebra
+	for i := 0; i < 2; i++ {
+		diff[i] = c.SubExtension(a[i], b[i])
+	}
+
+	return diff
+}

plonky2_verifier/arithmetic_extension_gate.go

@@ -0,0 +1,62 @@
+package plonky2_verifier
+
+import (
+	"fmt"
+	. "gnark-plonky2-verifier/field"
+)
+
+// Ideally, this should be serialized in the plonky2 repo
+const d = 2
+
+type ArithmeticExtensionGate struct {
+	numOps uint64
+}
+
+func NewArithmeticExtensionGate(numOps uint64) *ArithmeticExtensionGate {
+	return &ArithmeticExtensionGate{
+		numOps: numOps,
+	}
+}
+
+func (g *ArithmeticExtensionGate) Id() string {
+	return fmt.Sprintf("ArithmeticExtensionGate { num_ops: %d }", g.numOps)
+}
+
+func (g *ArithmeticExtensionGate) wiresIthMultiplicand0(i uint64) Range {
+	return Range{4 * d * i, 4*d*i + d}
+}
+
+func (g *ArithmeticExtensionGate) wiresIthMultiplicand1(i uint64) Range {
+	return Range{4*d*i + d, 4*d*i + 2*d}
+}
+
+func (g *ArithmeticExtensionGate) wiresIthAddend(i uint64) Range {
+	return Range{4*d*i + 2*d, 4*d*i + 3*d}
+}
+
+func (g *ArithmeticExtensionGate) wiresIthOutput(i uint64) Range {
+	return Range{4*d*i + 3*d, 4*d*i + 4*d}
+}
+
+func (g *ArithmeticExtensionGate) EvalUnfiltered(p *PlonkChip, vars EvaluationVars) []QuadraticExtension {
+	const0 := vars.localConstants[0]
+	const1 := vars.localConstants[1]
+
+	constraints := []QuadraticExtension{}
+	for i := uint64(0); i < g.numOps; i++ {
+		multiplicand0 := vars.GetLocalExtAlgebra(g.wiresIthMultiplicand0(i))
+		multiplicand1 := vars.GetLocalExtAlgebra(g.wiresIthMultiplicand1(i))
+		addend := vars.GetLocalExtAlgebra(g.wiresIthAddend(i))
+		output := vars.GetLocalExtAlgebra(g.wiresIthOutput(i))
+
+		mul := p.qeAPI.MulExtensionAlgebra(multiplicand0, multiplicand1)
+		scaled_mul := p.qeAPI.ScalarMulExtensionAlgebra(const0, mul)
+		computed_output := p.qeAPI.ScalarMulExtensionAlgebra(const1, addend)
+		computed_output = p.qeAPI.AddExtensionAlgebra(computed_output, scaled_mul)
+
+		diff := p.qeAPI.SubExtensionAlgebra(output, computed_output)
+		constraints = append(constraints, diff[0], diff[1])
+	}
+
+	return constraints
+}

plonky2_verifier/gate.go

@@ -57,22 +57,12 @@ func GateInstanceFromId(gateId string) gate {
 		}
 
 		matches := getRegExMatches(r, gateId)
-		numLimbsStr, hasNumLimbs := matches["numLimbs"]
-		baseStr, hasBase := matches["base"]
+		numLimbs, hasNumLimbs := matches["numLimbs"]
+		base, hasBase := matches["base"]
 		if !hasNumLimbs || !hasBase {
 			panic("Invalid BaseSumGate ID")
 		}
 
-		numLimbs, err := strconv.Atoi(numLimbsStr)
-		if err != nil {
-			panic("Invalid BaseSumGate ID: " + err.Error())
-		}
-
-		base, err := strconv.Atoi(baseStr)
-		if err != nil {
-			panic("Invalid BaseSumGate ID: " + err.Error())
-		}
-
 		return NewBaseSumGate(uint64(numLimbs), uint64(base))
 	}
 
@@ -86,41 +76,48 @@ func GateInstanceFromId(gateId string) gate {
 		}
 
 		matches := getRegExMatches(r, gateId)
-		bitsStr, hasBits := matches["bits"]
-		numCopiesStr, hasNumCopies := matches["numCopies"]
-		numExtraConstantsStr, hasNumExtraConstants := matches["numExtraConstants"]
+		bits, hasBits := matches["bits"]
+		numCopies, hasNumCopies := matches["numCopies"]
+		numExtraConstants, hasNumExtraConstants := matches["numExtraConstants"]
 		if !hasBits || !hasNumCopies || !hasNumExtraConstants {
 			panic("Invalid RandomAccessGate ID")
 		}
 
-		bits, err := strconv.Atoi(bitsStr)
-		if err != nil {
-			panic("Invalid RandomAccessGate ID: " + err.Error())
-		}
-
-		numCopies, err := strconv.Atoi(numCopiesStr)
-		if err != nil {
-			panic("Invalid RandomAccessGate ID: " + err.Error())
-		}
-
-		numExtraConstants, err := strconv.Atoi(numExtraConstantsStr)
-		if err != nil {
-			panic("Invalid RandomAccessGate ID: " + err.Error())
-		}
-
 		return NewRandomAccessGate(uint64(bits), uint64(numCopies), uint64(numExtraConstants))
 	}
 
+	if strings.HasPrefix(gateId, "ArithmeticExtension") {
+		// Has the format "ArithmeticExtensionGate { num_ops: 10 }"
+
+		regEx := "ArithmeticExtensionGate { num_ops: (?P<numOps>[0-9]+) }"
+		r, err := regexp.Compile(regEx)
+		if err != nil {
+			panic("Invalid ArithmeticExtensionGate regular expression")
+		}
+
+		matches := getRegExMatches(r, gateId)
+		numOps, hasNumOps := matches["numOps"]
+		if !hasNumOps {
+			panic("Invalid ArithmeticExtensionGate ID")
+		}
+
+		return NewArithmeticExtensionGate(uint64(numOps))
+	}
+
 	return nil
 	//panic(fmt.Sprintf("Unknown gate ID %s", gateId))
 }
 
-func getRegExMatches(r *regexp.Regexp, gateId string) map[string]string {
+func getRegExMatches(r *regexp.Regexp, gateId string) map[string]int {
 	matches := r.FindStringSubmatch(gateId)
-	result := make(map[string]string)
+	result := make(map[string]int)
 	for i, name := range r.SubexpNames() {
 		if i != 0 && name != "" {
-			result[name] = matches[i]
+			value, err := strconv.Atoi(matches[i])
+			if err != nil {
+				panic("Invalid field value for \"name\": " + err.Error())
+			}
+			result[name] = value
 		}
 	}
 

plonky2_verifier/gate_test.go

@@ -767,6 +767,7 @@ func TestGates(t *testing.T) {
 		{&BaseSumGate{numLimbs: 63, base: 2}, baseSumGateExpectedConstraints},
 		{&RandomAccessGate{bits: 4, numCopies: 4, numExtraConstants: 2}, randomAccessGateExpectedConstraints},
 		{&PoseidonGate{}, poseidonGateExpectedConstraints},
+		{&ArithmeticExtensionGate{numOps: 10}, arithmeticExtensionGateExpectedConstraints},
 	}
 
 	for _, test := range gateTests {

plonky2_verifier/vars.go

@@ -13,3 +13,12 @@ type EvaluationVars struct {
 func (e *EvaluationVars) RemovePrefix(numSelectors uint64) {
 	e.localConstants = e.localConstants[numSelectors:]
 }
+
+func (e *EvaluationVars) GetLocalExtAlgebra(wireRange Range) QEAlgebra {
+	// For now, only support degree 2
+	if wireRange.end-wireRange.start != 2 {
+		panic("Only degree 2 supported")
+	}
+
+	return QEAlgebra{e.localWires[wireRange.start], e.localWires[wireRange.end-1]}
+}